Various areas of aircraft structures are subject to ice formation in use and are therefore provided with anti-icing systems. One such area is an engine cowl inlet. The anti-icing system may use bleed air taken from the engine, for example from a compressor stage, to heat the nacelle inlet. The bleed air is typically controlled by a valve which limits the pressure of the air within the inlet so as to avoid damage to the inlet. The air bleed system may also incorporate a shut-off valve for safety purposes.
It would be desirable to provide an anti-icing system which has improved availability in the event of a valve failure.